Revealed the secret of a pulsar

An international team of astronomers and astronomers has discovered the origin of a’s strange behavior Press. Thanks to an observation campaign with 12 telescopesBoth on the ground and in space, including three European Southern Observatory (ESO) facilities, the team found that these sudden changes are due to sudden ejections of matter from the pulsar over very short timescales.

“We have witnessed extraordinary cosmic events where massive amounts of matter, akin to cosmic cannonballs, are ejected into space in a very short time, tens of seconds, from a small, dense celestial object spinning at incredibly high speeds.”, explained Maria Cristina BaglioResearcher at the University of New York Abu Dhabi, member of the Italian National Institute for Astrophysics (INAF) and lead author of the article published today astronomy and astrophysics.

We observe extraordinary cosmic events in which enormous amounts of matter, similar to cosmic cannonballs, are hurled into space in a very short time.

Maria Cristina Baglio (NYU Abu Dhabi)

A pulsar is a rapidly rotating, magnetic, dead star that emits a beam of electromagnetic radiation into space. As it spins, this ray traverses the cosmos (just like a lighthouse ray) and is spotted by the astronomical community as it crosses the line of sight we see from Earth. This makes the star’s brightness appear to pulse when viewed from our planet.

The authors focused on that PSR J1023+0038 or J1023 in short, a special type of pulsar with strange behavior. It is located about 4,500 light-years away in the constellation Sextant and orbits another star. For the past decade, the pulsar has been actively removing material from this companion. This material has accumulated in a disk around the pulsar and is slowly falling towards it.

As this process of accumulation of matter began, the light beam practically disappeared and the pulsar began to switch between two modes intermittently. In “high” mode, the pulsar emits bright X-rays, ultraviolet and visible light, while in “low” mode it is weaker at these frequencies and emits more radio waves. The pulsar can stay in each mode for several seconds or minutes and then switch to the other mode in just a few seconds. These changes have so far confused the astronomical community.

Twelve ground and space telescopes

“Our unprecedented observing campaign designed to understand the behavior of this pulsar involved a dozen state-of-the-art ground and space telescopes,” he says. Francesco Coti ZelatiResearcher at the Institute of Space Sciences (ICE-CSIC, Barcelona, ​​​​​​Spain) and co-lead author of the article.

The campaign included ESO’s Very Large Telescope (VLT) and New Technology Telescope (NTT), which detected visible and near-infrared light, and the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner. Over two nights in June 2021, they watched the system make more than 280 transitions between its high and low modes.

“We found that the mode change is due to a complicated interaction between the pulsar wind, a stream of high-energy particles moving away from the pulsar, and the matter flowing into the pulsar,” says Coti Zelati, who is also a member of the INAF.

In low mode, matter entering the pulsar is ejected in a narrow jet perpendicular to the disk. Gradually, this matter accumulates closer and closer to the pulsar, being rocked by the pulsing star’s winds, causing the matter to heat up. This puts the system into high mode, glowing brightly in X-ray, ultraviolet, and visible light. Eventually, these masses of hot matter are removed from the pulsar by the jet. With less hot matter on the disk, the system shines less brightly and reverts to low mode.

While this discovery has solved the mystery of J1023’s odd behavior, the astronomical community still has much to learn from studying this unique system, and ESO telescopes will continue to help observe this peculiar pulsar. In particular, ESO’s Extremely Large Telescope (ELT), currently under construction in Chile, will provide unprecedented insight into J1023’s switching mechanisms.

“The ELT will allow us to obtain important information on how the abundance, distribution, dynamics and energy of the matter inflowing around the pulsar is affected by the mode switching behavior,” he concludes. Sergio CampanaResearch Director of the INAF Brera Observatory and co-author of the study.


MC Baglio et al. “Ejecta behind the peaks and troughs of the transitional millisecond pulsar PSR J1023+0038”. astronomy and astrophysics2023

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